Prediction of fluid responsiveness in spontaneously breathing patients

Fluid therapy in the acute brain injured patient

Adequate fluid therapy in the acute brain injured (ABI) patient is essential for maintaining an adequate brain and systemic physiology and preventing intra- and extracranial complications. The target of euvolemia, implying avoidance of both hypovolemia and fluid overloading (or "hypervolemia," by definition associated with fluid extravasation leading to tissue edema) is of key importance. Primary brain injury can be aggravated by secondary brain injury and systemic deterioration through diverse pathways which can challenge appropriate fluid management, e.g. neuroendocrine and electrolyte disorders, stress cardiomyopathy (also known as cardiac stunning) and neurogenic pulmonary edema. This is an updated expert opinion aiming to provide a practical overview on fluid therapy in the ABI patient, partly based on more recent work and stressing the fact that intravenous fluids should be regarded as drugs, with their inherent potential for both benefit and (unintended) harm.

A critical review of the perioperative fluid therapy and hemodynamic monitoring recommendations of the Enhanced Recovery of the Adult Pathway (RICA): A position statement of the fluid therapy and hemodynamic monitoring Subcommittee of the Hemostasis, Transfusion Medicine and Fluid Therapy Section (SHTF) of the Spanish Society of Anesthesiology and Critical Care (SEDAR)

In an effort to standardize perioperative management and improve postoperative outcomes of adult patients undergoing surgery, the Ministry of Health, through the Spanish Multimodal Rehabilitation Group (GERM), and the Aragonese Institute of Health Sciences, in collaboration with multiple Spanish scientific societies and based on the available evidence, published in 2021 the Spanish Intensified Adult Recovery (RICA) guideline. This document includes 12 perioperative measures related to fluid therapy and hemodynamic monitoring. Fluid administration and hemodynamic monitoring are not straightforward but are directly related to postoperative patient outcomes. The Fluid Therapy and Hemodynamic Monitoring Subcommittee of the Hemostasis, Transfusion Medicine and Fluid Therapy Section (SHTF) of the Spanish Society of Anesthesiology and Critical Care (SEDAR) has reviewed these recommendations and concluded that they should be revised as they do not follow an adequate methodology.

Mock circulatory loop generated database for dynamic characterization of pressure-based cardiac output monitoring systems

Pulse contour cardiac output monitoring systems allow real-time and continuous estimation of hemodynamic variables such as cardiac output (CO) and stroke volume variation (SVV) by analysis of arterial blood pressure waveforms. However, evaluating the performance of CO monitoring systems to measure the small variations in these variables sometimes used to guide fluid therapy is a challenge due to limitations in clinical reference methods. We developed a non-clinical database as a tool for assessing the dynamic attributes of pressure-based CO monitoring systems, including CO response time and CO and SVV resolutions. We developed a mock circulation loop (MCL) that can simulate rapid changes in different parameters, such as CO and SVV. The MCL was configured to simulate three different states (normovolemic, cardiogenic shock, and hyperdynamic) representing a range of flow and pressure conditions. For each state, we simulated stepwise changes in the MCL flow and collected datasets for characterizing pressure-based CO systems. Nine datasets were generated that contain hours of peripheral pressure, central flow and pressure waveforms. The MCL-generated database is provided open access as a tool for evaluating dynamic characteristics of pressure-based CO algorithms and systems in detecting variations in CO and SVV indices. In an example application of the database, a CO response time of 10 s, CO and SVV resolutions with lower and upper limits of (-9.1%, 8.4%) and (-5.0%, 3.8%), respectively, were determined for a pressure-based CO benchtop system. This tool will support a more comprehensive assessment of pressure-based CO monitoring systems and algorithms.

Dynamic changes of pulse pressure but not of pulse pressure variation during passive leg raising predict preload responsiveness in critically ill patients with spontaneous breathing activity

PURPOSE

To evaluate whether the changes in arterial pulse pressure (PP) and/or pulse pressure variation (PPV) during passive leg raising (PLR) can be used to evaluate preload responsiveness in patients with spontaneous breathing activity.

MATERIALS AND METHODS

Patients ventilated with pressure support mode or totally spontaneously breathing were prospectively included. The values of PP and PPV were recorded before and at the end of PLR. The changes in cardiac index (CI) or the velocity-time integral (VTI) of the left ventricular outflow tract during PLR were tracked by the pulse contour analysis or transthoracic echocardiography. Patients exhibiting an increase in CI ≥ 10% or VTI ≥ 12% during PLR were defined as preload responders.

RESULTS

Among 33 patients included, 28 (80%) received norepinephrine and 14 were preload responders. The increase in PP > 2 mmHg in absolute value (4% in percentage) during PLR (PLR_PP) predicted preload responsiveness with an area under the receiver operating characteristic (AUROC) of 0.76 ± 0.09 (p = 0.003 vs. AUROC of 0.5). The changes in PPV during PLR, however, failed to predict preload responsiveness (p = 0.82 vs. AUROC of 0.5).

CONCLUSION

In patients with full spontaneous breathing activity, PLR-induced changes in PP had a fair ability to assess preload responsiveness even when norepinephrine was administered.

REGISTRATION NUMBER

ClinicalTrials.gov (NCT04369027).

Effective hemodynamic monitoring

Hemodynamic monitoring is the centerpiece of patient monitoring in acute care settings. Its effectiveness in terms of improved patient outcomes is difficult to quantify. This review focused on effectiveness of monitoring-linked resuscitation strategies from: (1) process-specific monitoring that allows for non-specific prevention of new onset cardiovascular insufficiency (CVI) in perioperative care. Such goal-directed therapy is associated with decreased perioperative complications and length of stay in high-risk surgery patients. (2) Patient-specific personalized resuscitation approaches for CVI. These approaches including dynamic measures to define volume responsiveness and vasomotor tone, limiting less fluid administration and vasopressor duration, reduced length of care. (3) Hemodynamic monitoring to predict future CVI using machine learning approaches. These approaches presently focus on predicting hypotension. Future clinical trials assessing hemodynamic monitoring need to focus on process-specific monitoring based on modifying therapeutic interventions known to improve patient-centered outcomes.

Prediction of fluid responsiveness. What’s new?

Although the administration of fluid is the first treatment considered in almost all cases of circulatory failure, this therapeutic option poses two essential problems: the increase in cardiac output induced by a bolus of fluid is inconstant, and the deleterious effects of fluid overload are now clearly demonstrated. This is why many tests and indices have been developed to detect preload dependence and predict fluid responsiveness. In this review, we take stock of the data published in the field over the past three years. Regarding the passive leg raising test, we detail the different stroke volume surrogates that have recently been described to measure its effects using minimally invasive and easily accessible methods. We review the limits of the test, especially in patients with intra-abdominal hypertension. Regarding the end-expiratory occlusion test, we also present recent investigations that have sought to measure its effects without an invasive measurement of cardiac output. Although the limits of interpretation of the respiratory variation of pulse pressure and of the diameter of the vena cava during mechanical ventilation are now well known, several recent studies have shown how changes in pulse pressure variation itself during other tests reflect simultaneous changes in cardiac output, allowing these tests to be carried out without its direct measurement. This is particularly the case during the tidal volume challenge, a relatively recent test whose reliability is increasingly well established. The mini-fluid challenge has the advantage of being easy to perform, but it requires direct measurement of cardiac output, like the classic fluid challenge. Initially described with echocardiography, recent studies have investigated other means of judging its effects. We highlight the problem of their precision, which is necessary to evidence small changes in cardiac output. Finally, we point out other tests that have appeared more recently, such as the Trendelenburg manoeuvre, a potentially interesting alternative for patients in the prone position.

Comparison of subclavian vein to inferior vena cava collapsibility by ultrasound in acute heart failure: A pilot study

BACKGROUND

Management of acute decompensated heart failure (ADHF) requires accurate assessment of relative intravascular volume, which may be technically challenging. Inferior vena cava (IVC) collapsibility with respiration reflects intravascular volume and right atrial pressure (RAP). Subclavian vein (SCV) collapsibility may provide an alternative.

HYPOTHESIS

The purpose of this study was to examine the relationship between SCV collapsibility index (CI) and IVC CI in ADHF.

METHODS

This was a prospective study of non-ventilated patients with ADHF who had paired IVC and SCV ultrasound assessments. As SCV CI is highly position-dependent, measurements were performed supine at 30-45°.

RESULTS

Thirty-three patients were included with 36 encounters. The sample size was adequately powered for receiver-operator characteristic (ROC) analysis. SCV CI correlated with IVC CI during relaxed breathing (R = .65, n = 36, p < .001) and forced inhalation (R = .47, n = 36, p = .0036). SCV CI < 22% and >33% corresponded to IVC CI < 20% and >50% suggesting hypervolemia (sensitivity/specificity: 72%) and hypovolemia (sensitivity/specificity: 78%), respectively. Moderate to severe tricuspid regurgitation (TR) compared to less than moderate TR was associated with lower SCV CI (medians: 12.4% vs. 25.3%, p = .022) and IVC CI (medians: 9.6% vs. 35.6%, p = .0012). SCV CI and IVC CI were not significantly different among chronic kidney disease stages.

CONCLUSION

In non-ventilated ADHF, SCV CI at 30-45° correlates with paired IVC CI, and may provide an alternative to IVC CI for assessment of relative intravascular volume, which may facilitate clinical management. Moderate to severe TR decreases SCV CI and IVC CI and may result in overestimation of relative intravascular volume.

Management of sepsis and septic shock in the emergency department

Early management of sepsis and septic shock is crucial for patients' prognosis. As the Emergency Department (ED) is the place where the first medical contact for septic patients is likely to occur, emergency physicians play an essential role in the early phases of patient management, which consists of accurate initial diagnosis, resuscitation, and early antibiotic treatment. Since the issuing of the Surviving Sepsis Campaign guidelines in 2016, several studies have been published on different aspects of sepsis management, adding a substantial amount of new information on the pathophysiology and treatment of sepsis and septic shock. In light of this emerging evidence, the present narrative review provides a comprehensive account of the recent advances in septic patient management in the ED.

Does respiratory variation in inferior vena cava diameter predict fluid responsiveness in adult patients? A systematic review and meta-analysis of diagnostic accuracy studies

Objectives:

To systematically review the diagnostic utility of the respiratory variation of the inferior vena cava diameter measured using ultrasonography for predicting fluid responsiveness in adult patients and compare the three commonly used equations, inferior vena cava distensibility, inferior vena cava collapsibility and inferior vena cava variability.

Methods:

We searched PubMed, Scopus, Web of Science and Cochrane library, and included studies investigating the diagnostic accuracy of the respiratory variation of the inferior vena cava measured using ultrasonography compared to a reference standard for measuring cardiac output after a fluid challenge for fluid responsiveness, and stratified participants as fluid responsive or not. We included studies conducted in the emergency department or intensive care unit. We excluded studies on paediatric, prehospital, cancer, pregnant, dialysis patients or healthy volunteers.

Results:

We retrieved 270 records and excluded 171 because of irrelevance, patient population or publication type. We screened the abstracts of 99 studies and then the full texts of 42 studies. Overall, 21 studies with 1321 patients were included, of whom 689 (52%) were fluid responsive. The mean threshold value for positive inferior vena cava distensibility, inferior vena cava collapsibility and inferior vena cava variability was 17%, 35% and 12%, respectively. The heterogeneity between studies was high. Bivariate diagnostic random-effects meta-analysis was used to calculate the summary receiver operating characteristics curves. The overall accuracy, sensitivity and specificity of respiratory variation of the inferior vena cava diameter were 0.85, 0.72 and 0.81, respectively. The accuracy of inferior vena cava distensibility and inferior vena cava collapsibility was similar. The diagnostic utility of respiratory variation of the inferior vena cava diameter was lower but not statistically significant in mechanically ventilated patients compared with spontaneous breathing for predicting fluid responsiveness.

Conclusion:

The respiratory variation of the inferior vena cava diameter has moderate diagnostic utility for predicting fluid responsiveness independent of the equation used.

Inferior Vena Cava Collapsibility Index: Clinical Validation and Application for Assessment of Relative Intravascular Volume

Accurate assessment of relative intravascular volume is critical to guide volume management of patients with acute or chronic kidney disorders, particularly those with complex comorbidities requiring hospitalization or intensive care. Inferior vena cava (IVC) diameter variability with respiration measured by ultrasound provides a dynamic noninvasive point-of-care estimate of relative intravascular volume. We present details of image acquisition, interpretation, and clinical scenarios to which IVC ultrasound can be applied. The variation in IVC diameter over the respiratory or ventilatory cycle is greater in patients who are volume responsive than those who are not volume responsive. When 2 recent prospective studies of spontaneously breathing patients (n = 214) are added to a prior meta-analysis of 181 patients, for a total of 7 studies of 395 spontaneously breathing patients, IVC collapsibility index (CI) had a pooled sensitivity of 71% and specificity of 81% for predicting volume responsiveness, which is similar to a pooled sensitivity of 75% and specificity of 82% for 9 studies of 284 mechanically ventilated patients. IVC maximum diameter <2.1 cm, that collapses >50% with or without a sniff is inconsistent with intravascular volume overload and suggests normal right atrial pressure (0-5 mmHg). Inferior vena cava collapsibility (IVC CI) < 20% with no sniff suggests increased right atrial pressure and is inconsistent with overt hypovolemia in spontaneously breathing or ventilated patients. These IVC CI cutoffs do not appear to vary greatly depending on whether patients are breathing spontaneously or are mechanically ventilated. Patients with lower IVC CI are more likely to tolerate ultrafiltration with hemodialysis or improve cardiac output with ultrafiltration. Our goal for IVC CI generally ranges from 20% to 50%, respecting potential biases to interpretation and overriding clinical considerations. IVC ultrasound may be limited by factors that affect IVC diameter or collapsibility, clinical interpretation, or optimal visualization, and must be interpreted in the context of the entire clinical situation.